a) Field of the Invention
The present invention relates to apparatus and method for performing an automatic control over a velocity f an automotive vehicle in which the apparatus is mounted o as to maintain an inter-vehicle distance from the vehicle to another vehicle running ahead of the vehicle to follow up the other vehicle.
b) Description of the Related Art
A Japanese Patent Application First Publication No. Showa 60-121130 published on Jun. 28, 1985 exemplifies a first previously proposed vehicular velocity controlling apparatus.
In the first previously proposed vehicular velocity controlling apparatus disclosed in the above-identified Japanese Patent Application First Publication, a vehicular velocity of the vehicle is detected, a safe inter-vehicle distance is calculated on the basis of the detected vehicular velocity, an actual inter-vehicle distance from the vehicle to a preceding vehicle which is running ahead of the vehicle is calculated, a variation rate of the inter-vehicle distance per predetermined time is calculated from the detected Inter-vehicle distance, the safe inter-vehicle distance is corrected according to the variation rate of the inter-vehicle distance, and the vehicular velocity of the vehicle is adjusted according to a difference between the corrected safe inter-vehicle distance and the actual inter-vehicle distance.
Since, in the first previously proposed vehicular velocity controlling apparatus, the vehicular velocity is determined only from the safe inter-vehicle distance and the actual inter-vehicle distance, a vehicular velocity of the vehicle does not always match with a sense of a vehicular occupant(s) and a disagreeable feeling is left to the vehicular occupant when a relationship of the vehicle to the preceding vehicle is abruptly changed in such a way that another vehicle which has run on another traffic lane is interrupted before the vehicle or that the vehicle has made a traffic lane change to another traffic lane.
To solve the above-described dismatch with the sense of the vehicular occupant(s) and disagreeable feeling left to him, second, third, and fourth vehicular velocity controlling apparatuses have been proposed.
A Japanese Patent Application First Publication No. Heisei 7-89367 published on Apr. 4, 1995 exemplifies the second previously proposed vehicular velocity controlling apparatus.
A Japanese Patent Application First Publication No. Heisei 5-156975 published on Jun. 22, 1993 exemplifies the third previously proposed vehicular velocity controlling apparatus.
A Japanese Patent Application First Publication No. Heisei 5-159198 published on Jun. 25, 1993 exemplifies the fourth previously proposed vehicular velocity controlling apparatus.
In the second previously proposed vehicular velocity controlling apparatus, such a preceding vehicle follow-up run control that the vehicular velocity is adjusted so that the inter-vehicle distance from the vehicle to the preceding vehicle which is running ahead of the vehicle on the same traffic lane gives a predetermined value is carried out and, in addition to this, a cruise speed control such that a constant vehicular velocity run at a preset set vehicular velocity is carried out if no preceding vehicle is trapped. Then, when another vehicle is interrupted before the vehicle under the follow-up run control or under the cruise speed control, control is transferred to such a special interrupt control that an engine throttle valve is completely closed for a constant period of time to effect an engine braking so that the vehicle is moderately decelerated. Consequently, the interrupt vehicle can smoothly be interposed in a front area of the vehicle on the same traffic lane as the vehicle.
In the third previously proposed vehicular velocity controlling apparatus, a target value of the inter-vehicle distance is calculated on the basis of the vehicular velocity and a relative velocity of the vehicle to the preceding vehicle and the vehicular velocity of the vehicle is adjusted so that the vehicular velocity is made congruent with the target value of the inter-vehicle distance.
In a case where a deceleration control to decelerate the vehicle is carried out due to the interrupt of the other vehicle, the deceleration control is halted even if the inter-vehicle distance is below the target value of the inter-vehicle distance in a case where this deceleration control is equal to or above a predetermined value or in a case where the deceleration control is continued for a predetermined period of time and a vehicular velocity variation control is carried out to make the vehicular velocity of the vehicle equal to that of the preceding vehicle.
Furthermore, in the fourth previously proposed vehicular velocity controlling apparatus, suppose that the vehicle makes a traffic lane change from a normal running lane to an over-head lane to overhead the preceding vehicle. In this case, the inter-vehicle distance to the preceding vehicle after the traffic lane change is modified as the target value of the inter-vehicle distance and the inter-vehicle distance is maintained within a time duration to the end of the over-head motion of the vehicle.
After the end of the over-head motion of the vehicle, the inter-vehicle distance is extended gradually with time to the normally determined target value of the inter-vehicle distance.
Hence, the inter-vehicle distance after the lane change is maintained and a quick approach to the vehicle from a following vehicle which is running behind the vehicle can be prevented.